Paleontology, Evolutionary Developmental Biology
The fossil record empirically shows heterogeneous patterns of morphological diversification in evolution: morphological evolution has seen arrested and rapid phases in the past. In other words, evolutionary rates and diversity in morphology have not been homogeneous in geological time scale, and "evolvability" appears to vary by phylogenetic position. Such evolutionary patterns must be governed both by adaptation (external factor) and by developmental constraints, or limitations of directions and ranges in evolutionary change caused by characteristics of developmental systems (internal factor). However, the conventional paleontological studies have focused only on the external factor, and it remains unclear how the developmental constraints have affected the evolutionary pattern. On the other hand, in evolutionary developmental biology (evo-devo), scientists have not paid attention to extinctions, which act as evolutionary "pruning." In particular, possibilities that mass extinction produced the bases for developmental constraints and that specific lineages rapidly diversified after mass extinctions possessed more "evolvable" characteristics of developmental systems than those of other lineages are open questions.
1. Hirasawa T., et al. (2022) Morphology of Palaeospondylus shows affinity to tetrapod ancestors. Nature, 606: 109–112.